The present invention relates in general to a surface texturing process, and more particularly, to a pretreatment process performed prior to performing a surface texturing process wherein irregularities are produced on a surface to be textured using an ion beam.
Surface texturing has many applications in electron sources, electric bonding, solar cells, optics and display devices. One of the most commonly used technologies for surface texturing is ion beam sputtering. The details of this process are described in Cone Formation as a Result of Whisker Growth on Ion Bombarded Metal Surfaces, G. K. Wehner, J. Vac. Sci. Technol. A3(4), pp. 1821-1834 (1985) and Cone Formation on Metal Targets During Sputtering, G. K. Wehner, J. Appl. Phys., Vol. 42, No. 3, pp. 1145-1149 (Mar. 1, 1971), which are hereby incorporated by reference herein, which teach that a cone (micro-tip) structure may be produced by using an ion source for etching a material, such as copper, after it has been seeded with a second material, such as molybdenum. An improvement upon this process is the subject of the above cross-referenced patent application, wherein a dual ion beam system is utilized to efficiently control the ion beam sputtering process.
For many applications, it is required that the surface textured structure be uniform in terms of the density, height and shape of the resultant cones. Additionally, for mass production manufacturing, the process should be controllable and repeatable. However, the above-noted surface texturing process using ion beam sources is difficult to control, and the structures of the cones are not as uniform as many applications require, such as for flat panel display devices.
Thus, there is a need in the art for a surface texturing process that is controllable, repeatable, and produces a uniformity of resultant cones.
The aforementioned need is satisfied by the present invention, which forms micro-tip structures (throughout this document xe2x80x9cmicro-tipxe2x80x9d and xe2x80x9cconexe2x80x9d are used interchangeably) at or near the locations upon which an irregularity has been formed in the surface of a material.
Thus, when forming micro-tips, a material layer is deposited upon a substrate. An irregularity is then formed in the surface of the material prior to loading the sample into an evacuated chamber to be subject to an ion milling process. The ion milling process sputters a seed material onto the surface of the material. An ion beam is then utilized to etch the material, resulting in cones or micro-tips being formed thereon. The irregularities are nuclei sites for collecting the seed material.
An irregularity may be formed by polishing the surface with a polishing solution, such as a diamond spray.
Alternatively, an irregularity may be formed by bombarding the surface through a sandblasting technique.
Alternatively, an irregularity may be formed using a photolithography technique, whereby a step feature is caused to be formed on the surface of the material.
Alternatively, an irregularity may be formed through a mechanical means, such as by scratching the surface with a needle.
In a preferred embodiment of the present invention, a dual ion beam system is utilized whereby one ion beam source is used to sputter the seed material onto the surface of the material, while a second ion beam source is utilized for the etching portion of the process.
In one embodiment of the present invention, the material upon which the irregularities are formed is an emitter material that may be utilized in a field emission device, wherein electrons are emitted from the formed micro-tips under the influence of a potential field.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.